How to Calculate Topsoil Cost — Step by Step

The short answer

To work out what topsoil costs, measure the area, work out the volume, turn it into cubic yards, add 10% extra, and multiply by the price per cubic yard. For a 500 square foot bed at 3 inches deep that gives a volume of 125.00 cubic feet, which is 4.63 cubic yards, and with 10% extra it is 5.09 cubic yards to order. The topsoil costs $203.70 at $40.00 a cubic yard, plus $50.00 delivery, which is $253.70 in total.

The three numbers that matter

The first number is the area, in square feet, measured across the bed. For this bed that is 500 square feet. The second number is the depth, which is 3 inches for a new bed and 1 inch for a topdress. The third number is the price per cubic yard, which is about $40.00 for topsoil. The volume is 500 times 3 divided by 12, which is 125.00 cubic feet, and the raw yards are 125.00 divided by 27, which is 4.63 cubic yards.

The billable yards are the raw yards plus 10% extra, which is 4.63 times 1.10, which is 5.09 cubic yards to order. The topsoil cost is the billable yards times the price per cubic yard, which is 5.09 times $40.00, which is $203.70. The total is the topsoil cost plus the delivery, which is $203.70 plus $50.00, which is $253.70. The check is the cost per square foot: $253.70 divided by 500 is $0.51, the number to compare between beds and between quotes. If a quote is far from $0.51 a square foot for the same bed, ask what is different.

The method

The method is three steps and an addition. One: multiply the area by the depth and divide by 12, to get the volume in cubic feet. Two: divide the volume by 27, to get the raw cubic yards, then multiply by one plus the extra, to get the billable yards. Three: multiply the billable yards by the price per cubic yard, to get the topsoil cost, then add the delivery, to get the total. The extra is the part people forget, and it is the part that leaves the last corner of the bed bare.

Step by step

Step 1: find the area. Measure the bed in feet, with a tape measure, and multiply the length by the width. For this bed that is 500 square feet. A bed that follows a curve is measured in pieces, and the pieces are added up, because the straight-line distance is not the bed.

Step 2: find the volume. Multiply the area by the depth in inches and divide by 12. For this bed that is 500 times 3 divided by 12, which is 125.00 cubic feet. The 12 turns inches into feet.

Step 3: find the billable yards. Divide the volume by 27, because a cubic yard is 27 cubic feet, then multiply by one plus the extra. For this bed that is 125.00 divided by 27, which is 4.63 cubic yards, and 4.63 times 1.10, which is 5.09 cubic yards to order. The extra is 10% for a normal bed, and 15% for a bed with a deep edge.

Step 4: price the topsoil. Multiply the billable yards by the price per cubic yard. For this bed that is 5.09 times $40.00, which is $203.70. The price is worked out from the unrounded billable yards, not the rounded 5.09 cubic yards, so the arithmetic is exact.

Step 5: add the delivery. Add the delivery to the topsoil cost, to get the total. For this bed that is $203.70 plus $50.00, which is $253.70 in total. The check is the cost per square foot: $253.70 divided by 500 is $0.51, the number to compare between beds and between quotes.

Step 6: count the bags and the weight. Multiply the billable yards by 27, then round up to whole bags. For this bed that is 5.09 times 27, which is 137.5 cubic feet, so it takes 138 bags, which would cost $552.00 at $4.00 a bag. The weight is 5.09 times 2,000, which is 10,185 pounds, or 5.09 tons.

The worked example

A homeowner is topping up a 500 square foot garden bed, 3 inches deep, and the soil yard charges $40.00 a cubic yard for topsoil, and $50.00 for delivery. The volume is 500 times 3 divided by 12, which is 125.00 cubic feet. The raw yards are 125.00 divided by 27, which is 4.63 cubic yards, and with 10% extra the billable yards are 5.09 cubic yards to order. The topsoil costs 5.09 times $40.00, which is $203.70, and the total is $253.70, or $0.51 a square foot. The soil would take 138 bags, which would cost $552.00, so bulk wins by $298.30. The load weighs about 10,185 pounds, and it comes on a truck, not in a car boot.

A bigger bed, and other round numbers

A 1,000 square foot bed is 1,000 times 3 divided by 12, which is 250.00 cubic feet, so the raw yards are 9.26 cubic yards and the billable yards are 10.19 cubic yards, so the topsoil costs $407.41 and the total is $457.41, or $0.46 a square foot. A bed 2 inches deep is 83.33 cubic feet, so the raw yards are 3.09 cubic yards and the billable yards are 3.40, so the topsoil costs $135.80 and the total is $185.80. Topsoil at $55.00 a cubic yard costs $280.09, and the total is $330.09. Topsoil with no delivery is $203.70, or $0.41 a square foot.

Working backwards from a budget

To find how much bed a budget covers, subtract the delivery from the budget, then divide what is left by the price per cubic yard, then divide by the extra, then turn the yards back into square feet. A $300 budget minus the $50 delivery leaves $250. Divide that by $40.00 a cubic yard, and it buys 6.25 billable cubic yards. Divide by 1.10, and it is 5.68 raw cubic yards, which is 153.41 cubic feet. Divide by the depth in feet, 0.25, and it is 613.64 square feet of bed. A $500 budget buys 1,104.55 square feet.

Common mistakes

The most common mistake is ordering the raw yards, not the billable yards. A 500 square foot bed at 3 inches deep is 5.09 cubic yards to order, not 4.63, so ordering the raw yards leaves the last corner bare by almost half a cubic yard. The second mistake is forgetting the delivery, which is $50.00. The third is measuring the straight-line distance instead of the bed. The fourth is spreading the topsoil a week after it arrives, which lets it dry out and weeds grow in it. The fifth is guessing the extra: 5% looks the same as 10% on the day, but the last corner comes up short.

The verdict

A 500 square foot bed at 3 inches deep costs $253.70 in topsoil: 5.09 cubic yards to order, at $40.00 a cubic yard, plus $50.00 delivery. Measure the area, work out the cubic yards, add 10% extra, and price the yards. Check the numbers on the topsoil cost calculator, the mulch cost calculator, or the gravel cost calculator.